The present invention related to an image-forming apparatus such as an electrophotographic device, an electrostatic recording device, to an image-forming method using such an image-forming apparatus, and to a developing agent to be used in such an image-forming apparatus.
As a method of fixing a toner image, after being transferred to a recording material, and the toner image having been obtained through the development of an electrostatic latent image formed on an image carrier, there are conventionally known various method such as a heat fixing method, a pressure fixing method, a flash fixing method, a high-frequency heat fixing method, an electromagnetic induction heating method, etc.
In particular, according to the electromagnetic induction heating method, an electric current is passed through a coil wound around a core, thereby generating Joule heat in concurrent with a magnetic field, the resultant Joule heat being utilized as a heat source for the fixing. With respect to the technique using this electromagnetic induction heating method, Japanese Patent Unexamined Publication S52-139435 discloses a method wherein the heating is performed by making use of fixing means using a combination of a coil constructed as mentioned above and a heating element. This fixing means however is accompanied with a problem that due to the generation of non-uniformity of temperature distribution in the heating element, it is difficult to obtain an image of stabilized image concentration.
Further, Japanese Patent Unexamined Publication H1-134385 discloses a fixing method using the electromagnetic induction heating method, wherein a one-component magnetic toner comprising a combination of metallic or magnetic particle and a thermoplastic resin is employed.
According to this fixing method, the metallic or magnetic particle in a toner is allowed to develop heat through an electromagnetic induction heating, thereby causing the thermoplastic resin in the toner to melt and to achieve the fixing. Therefore, only the portions required can be selectively heated, thus making it possible to shorten the warm-up time. Further, since the surrounding parts and devices are not heated up in a substantial degree, there is no need to take the temperature rise of these surrounding parts and devices into consideration. Additionally, it is possible to make the fixing system much smaller.
This fixing method however is defective in that the one-component magnetic toner containing a large quantity of magnetic power tends to scatter at the step of fixing due to an influence of magnetic field, thereby disturbing the image being fixed. Further, this fixing method however is accompanied with a problem that the toner cannot be used in a binary developing system.
The present invention has been accomplished in view of the aforementioned circumstances, and therefore, a first object of the present invention is to provide a developing agent which is suited for use in an electromagnetic induction heating system and which enables to obtain an excellent image of stabilized image concentration.
A second object of the present invention is to provide an image-forming apparatus adapted for use in an electromagnetic induction heating system, which is small in size, is capable of shortening the warm-up time thereof as well as capable of saving energy consumption, and enables to obtain an excellent image of stabilized image concentration.
A third object of the present invention is to provide an image-forming method which enables to miniaturize an apparatus involved, to shorten the warm-up time, to save energy consumption, and to obtain an excellent image of stabilized image concentration.
According to a first aspect of the present invention, there is provided a developing agent comprising a toner particle containing a binder resin having an acid value of 1 to 30, a glass transition temperature of 40 to 65xc2x0 C. and a softening point of 80 to 140xc2x0 C., an azo-based iron complex, and a colorant and/or a first magnetic particle.
According to a second aspect of the present invention, there is provided an image-forming apparatus comprising;
an image carrier;
a developing device for forming a developing agent image through a development of an electrostatic latent image formed on the image carrier, the developing device being disposed opposite to the image carrier and containing a developing agent comprising a toner particle containing a binder resin having an acid value of 1 to 30, a glass transition temperature of 40 to 65xc2x0 C. and a softening point of 80 to 140xc2x0 C., an azo-based iron complex, and a colorant and/or a first magnetic particle;
a transferring device for transferring the developing agent image onto a recording material; and
a fixing device of electromagnetic induction heating system for fixing the developing agent image transferred onto the recording material.
According to a third aspect of the present invention, there is provided an image-forming method which comprises the steps of;
forming an electrostatic latent image on an image carrier;
developing the electrostatic latent image with a developing agent comprising a toner particle containing a binder resin having an acid value of 1 to 30, a glass transition temperature of 40 to 65xc2x0 C. and a softening point of 80 to 140xc2x0 C., an azo-based iron complex, and a colorant and/or a first magnetic particle;
transferring a developing agent image thus developed onto a recording material; and
fixing the developing agent image onto the recording material by heating the developing agent image according to an electromagnetic induction heating system while pressing the developing agent image transferred onto the recording material.
According to the present invention, since there is employed a developing agent containing a binder resin having an acid value of 1 to 30, a glass transition temperature of 40 to 65xc2x0 C. and a softening point of 80 to 140xc2x0 C., and an azo-based iron complex in a fixing system utilizing an electromagnetic induction heating method, it is now possible to obtain a high-quality image of high-fidelity to a latent image.